1. Field of Invention
The present invention relates to a head cleaning method used in an inkjet printer to recover from defective discharge of ink droplets from the nozzles of an inkjet head, and relates to an inkjet printer implementing this head cleaning method.
2. Description of Related Art
Inkjet printers in particular are subject to discharge defects in the ink nozzles of the inkjet head. Such discharge defects include the nozzles becoming clogged by an increase in the viscosity of ink left in the nozzles as well as by air bubbles, dust, or other foreign matter getting into the nozzles, and nozzles that are not completely clogged but become unable to discharge the prescribed amount of ink at the prescribed position on the paper being printed. Nozzles in such a condition are called defective nozzles. Because print quality drops when an inkjet head having defective nozzles is used for printing, the inkjet head is moved regularly or at a predetermined time to a position outside the printing area and a head cleaning process is applied. The inkjet printer taught in Japanese Unexamined Patent Appl. Pub. JP-A-2003-1835, for example, can perform two head cleaning processes, a wiper cleaning process whereby ink on the nozzle surface is removed using a wiper, and a nozzle vacuuming process in which ink is removed from inside the nozzles by suction to prevent or recover from nozzle clogging.
The printer taught in Japanese Unexamined Patent Appl. Pub. JP-A-2007-7960, executes nozzle check and head cleaning processes as part of the startup procedure when the printer power turns on. This printer automatically runs the nozzle check process when the power turns on because the likelihood is high that ink had not been discharged from the nozzles for an extended period of time before the power turned on and the possibility that nozzles are clogged is therefore high. This printer also checks the number of defective nozzles found in the nozzle check, executes a head cleaning process controlled according to the number of defective nozzles if the number of defective nozzles is greater than or equal to a user-defined threshold value, and does not execute the head cleaning process if the number of defective nozzles is less than the set threshold value.
Japanese Unexamined Patent Appl. Pub. JP-A-2003-1835 does not propose checking the nozzles and executing a head cleaning process according to the condition of the nozzles, or executing a head cleaning process controlled according to the condition of the printer while the head is being cleaned.
Japanese Unexamined Patent Appl. Pub. JP-A-2007-7960 teaches cleaning the print head at a time when the possibility is high that there are clogged nozzles, for example, but is silent about changing the content of the cleaning process according to differences in nozzle condition, such as whether or not the likelihood is high that more nozzles than usual are clogged, such as whether or not it is immediately after the power turned on, or whether or not a direct impact was applied to the printer. This means that the cleaning process may be too gentle when the likelihood of there being numerous defective nozzles is high, the cleaning process may take too long to finish, or excessive ink may be consumed.